Description
A default route is advertised to a BGP speaker when no default route is found in the routing table.
Solution
Advertising a default route in BGP.
Adding the command set capability-default-originate enable will advertise a default route to the BGP peer without a default route present in the RIB. The default route will be created to be announced to the BGP neighbor only.
# config router bgp
set as 65002
set router-id 1.1.1.2
config neighbor
edit "1.1.1.1"
set capability-default-originate enable
set remote-as 65001
set send-community6 disable
next
end
config redistribute "connected"
end
config redistribute "rip"
end
config redistribute "ospf"
end
config redistribute "static"
end
config redistribute "isis"
end
config redistribute6 "connected"
end
config redistribute6 "rip"
end
config redistribute6 "ospf"
end
config redistribute6 "static"
end
config redistribute6 "isis"
end
No default route is visible in routing table. However, the route is advertised.
# Fortigate# get router info routing-table all
Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default
C 1.1.1.0/30 is directly connected, wan2
C 192.168.1.0/24 is directly connected, internal
Fortigate# get router info bgp neighbors 1.1.1.1
BGP neighbor is 1.1.1.1, remote AS 65001, local AS 65002, external link
BGP version 4, remote router ID 192.168.1.254
BGP state = Established, up for 00:45:11
Last read 00:00:56, hold time is 180, keepalive interval is 60 seconds
Configured hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
Route refresh: advertised and received (old and new)
Address family IPv4 Unicast: advertised and received
Address family IPv6 Unicast: advertised
Received 83 messages, 0 notifications, 0 in queue
Sent 91 messages, 2 notifications, 0 in queue
Route refresh request: received 1, sent 0
Minimum time between advertisement runs is 30 seconds
For address family: IPv4 Unicast.
# BGP table version 6, neighbor version 6
Index 1, Offset 0, Mask 0x2
AF-dependant capabilities:
Graceful restart: advertised
Community attribute sent to this neighbor (both)
Default information originate, default sent
0 accepted prefixes
1 announced prefixes
For address family: IPv6 Unicast.
# BGP table version 1, neighbor version 1
Index 1, Offset 0, Mask 0x2
0 accepted prefixes
0 announced prefixes
Connections established 6; dropped 5
Local host: 1.1.1.2, Local port: 179
Foreign host: 1.1.1.1, Foreign port: 61735
Nexthop: 1.1.1.2
Nexthop global: ::
Nexthop local: ::
BGP connection: non shared network
Last Reset: 00:46:54, due to BGP Notification sent
Notification Error Message: (CeaseUnspecified Error Subcode)
Fortigate # get router info bgp neighbors 1.1.1.1 advertised-routes
BGP table version is 6, local router ID is 1.1.1.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0/0 1.1.1.2 100 32768 i
Total number of prefixes 1
BGP Peer (in this case Cisco):
# Router#sho ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 1.1.1.2 to network 0.0.0.0
# 1.0.0.0/30 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Vlan1
B* 0.0.0.0/0 [20/0] via 1.1.1.2, 00:48:50
Router#sho ip bgp
BGP table version is 2, local router ID is 192.168.1.254
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0 1.1.1.2 0 65002 i 1.1.1.2 from 1.1.1.2 (1.1.1.2)
Origin IGP, localpref 100, valid, external, best
